Spray Foam the pipe down to the back of the foam tombstone, making sure not fill those bottom holes in.
Let that DRY! Then take some 1/2" EMT metal conduit and cut down. Make sure to make at least 1 feet longer then what you cut your PVC down too so you can stack into the ground. BE CAREFUL! I used a SAWZALL (Battery and Charger) to cut mine down with Metal Blade. Once your foam is completely dry you can spray paint the foam to blend it in, (This isn't necessary but is a nice added touch) Then slide the tombstone over the metal conduct. Enjoy!